For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
GOD created Adam and Eve because He wanted a family. It's as simple as that. Amen.
When you say the following it seems to say that you know all of the possibilities that were at God'd disposal: "it must mean that the fall of mankind was part of God's sovereign plan from the beginning. No other answer makes sense given what we have been saying thus far.'"
I think the word "must" should be replaced with "may" in your comment. And you should revise the last sentence above with "No other answer makes sense to me, given what we have been saying thus far.'"
Knowing something is going to happen is not the same as planning for it to happen. Parents know their children are going to trip and skin their knees and bloody their noses, but no parent plans for that to happen. If they prevented it from happening, they would prevent the child from learning by the experience.
NOT all will be saved by Christ as this goes against what Jesus teaches. Why did Jesus call His disciples to be fishers of men? This goes against the doctrine of predestination where Jesus has called us before time. The new testament clearly states that the rich man died and went to hell, so he did not go to Heaven. Lazarus, who had also died, was across the gulf with Abraham. The rich man cried out that he wanted Lazarus to cool his tongue as he was on fire.
False teaching is to be avoided and rebuked. Sin is very real, and Jesus abhors it in every way.
John 3:16 states "For God so loved the world that He gave His only Son, that whosoever believes in Him shall not die (ie everlasting damnation and torture in hell in complete isolation from God). It does not say all will believe otherwise Jesus would not have had to die for us as he would have accepted us all in our sin as fit for heaven , ABSOLUTELY NOT!
In Revelations it talks about the smoke from the tormented ones rising in front of The Almighty.
God already knows how it's going to end and He knows that He is Victorious. (Rev 20:10)
The fallen angel that is the devil, is a beast and as Genesis describes the serpent, which is a reptile. (Gen 3:1)